Place the stm32_cr4_fft_1024_lib folder into arduino/libraries

Heavily inspired by the STM32 Pig-o-scope (https://github.com/pingumacpenguin/STM32-O-Scope) , so the pin mappings are the same for the LCD.

The library can perform a 1024 sized int16 FFT in about 3 ms.